1. Field of the Invention
The present invention relates to multilayer ceramic electronic components and manufacturing methods thereof, and more particularly, to an improvement in the formation of terminal electrodes in a multilayer ceramic electronic component having a cover.
2. Description of the Related Art
A multilayer ceramic electronic component and a manufacturing method thereof are disclosed in Japanese Unexamined Patent Application Publication No. 8-37251. This publication describes the following method for manufacturing a multilayer ceramic electronic component.
A plurality of ceramic green sheets is first prepared, throughholes are formed in predetermined ceramic green sheets, and terminal via hole conductors are formed in the throughholes. The terminal via hole conductors may be a conductor filled in the throughhole or a conductor provided on the internal surface of the throughhole. In addition, on predetermined ceramic green sheets, wiring conductors, such as conductive films or via hole conductors other than the terminal via hole conductors described above, are formed.
Next, the ceramic green sheets are laminated to each other and are then pressed, thereby forming a green mother electronic component. This mother electronic component is formed such that when being divided along predetermined dividing lines, electronic component bodies for forming a plurality of multilayer ceramic electronic components are obtained.
Next, at locations where the terminal via hole conductors of the green mother electronic component are to be divided, penetrating holes are formed, and as a result, the terminal via hole conductors are exposed at the internal surfaces of the penetrating holes. In the step described above, one penetrating hole is formed for each terminal via hole conductor.
The green mother electronic component is fired. After firing is performed, a plating film composed of, for example, Ni/Au or Ni/Sn, is formed by wet plating on the terminal via hole conductor exposed at the internal surface of the penetrating hole.
Subsequently, elements are mounted on one major surface of the mother electronic component at which one major surface of each laminated ceramic body is formed.
Next, the mother electronic component is divided along the dividing lines passing through the penetrating holes. Accordingly, by dividing the terminal via hole conductors as described above, a plurality of the electronic component bodies is formed having terminal electrodes formed at main surfaces of notches which are formed by dividing the penetrating holes. The division described above is typically performed in a so-called chocolate-break manner via grooves formed in both major surfaces of the mother electronic component along the dividing lines. The grooves are formed before or after the firing of the mother electronic component.
Next, although not specifically disclosed in the publication described above, a cover is disposed such that an opening thereof faces the laminated ceramic body to cover the elements mounted thereon. In the case described above, since the notches provided with the terminal electrodes at the main surfaces thereof are formed by the division of the penetrating holes, as described above, at least one foot portion, to be disposed in at least one of the notches, is preferably provided on the cover. Hence, when the foot portion is disposed in the notch provided with ground terminal electrodes and is bonded thereto via soldering or other suitable material, the cover is fitted to the laminated ceramic body.
As described above, since the notches are formed in the laminated ceramic body, and the terminal electrodes are formed in these notches, when the cover is fitted to the laminated ceramic body, the following advantages can be obtained.
That is, first, since the foot portion is disposed in the notch, the cover can be easily positioned with respect to the laminated ceramic body.
In addition, since the foot portion and the ground terminal electrode are bonded to each other in the notch, solder used for bonding remains in the notch, and the solder is not likely to cause short-circuiting with another terminal electrode.
The multilayer ceramic electronic component thus formed is mounted on a wiring substrate through the terminal electrodes by soldering. However, when the soldering is performed to bond the foot portion to the ground terminal electrode, the solder provided therebetween may remelt when the soldering is performed for the wiring substrate as described above. In this case, the solder bonding the foot portion to the ground terminal electrode may melt and flow to another terminal electrode. However, since the ground terminal electrodes are formed in the notches, as described above, the solder is prevented from flowing out.
However, the conventional technique described above has the following problems that must be overcome.
First, problems occur when the alignment pitch of the terminal electrodes is decreased, for example, to 0.6 mm or less.
In order to decrease the alignment pitch of the terminal electrodes, in addition to a decrease in the diameter of the penetrating hole provided for dividing the terminal via hole conductor, the width thereof exposed at the internal surface of the penetrating hole must be decreased.
However, when the size of the penetrating hole is decreased, the flow of a wet plating solution used for plating the exposed area of the terminal electrode becomes inferior, and as a result, it is difficult to appropriately form the plating film. In addition, since the exposed width of the terminal via hole conductor is decreased, it is more difficult to form an appropriate plating film.
In addition, in order to decrease the alignment pitch of the terminal electrodes, the pitch of the penetrating holes must also be decreased. However, when the pitch described above is decreased, a portion between the adjacent penetrating holes is subject to breakage in a step of forming the penetrating hole or a firing step.
When the pitch of the penetrating holes is decreased, projections having a sawtooth shape are formed between the adjacent notches provided in the laminated ceramic body obtained by the division described above, and hence when the laminated ceramic body is handled, these sawtooth projections often cause chipping.
In addition, in order to form a greater number of the terminal electrodes, the number of the penetrating holes is increased, and as a result, the number of steps of forming the penetrating hole is also increased.
To overcome the problems described above, preferred embodiments of the present invention provide a greatly improved multilayer ceramic electronic component including a cover and a manufacturing method thereof.
A multilayer ceramic electronic component according to a preferred embodiment of the present invention includes a laminated ceramic body including a plurality of ceramic layers laminated on each other, in which a first major surface and a second major surface face each other, and first, second, third, and fourth side surfaces, each of which extends between the first and the second major surfaces. In this arrangement, the first and the third side surfaces face each other, and the second and the fourth side surfaces face each other.
First, second, third, and fourth notches are provided in the first, second, third, and fourth side surfaces, respectively, of the laminated ceramic body described above.
Ground terminal electrodes are provided at main surfaces of the first and third notches, and a plurality of terminal electrodes are arranged in parallel at a main surface of each of the second and fourth notches. The plurality of terminal electrodes disposed at the main surface of each of the second and fourth notches may include ground terminal electrodes electrically connected to the ground terminal electrodes provided at the main surfaces of the first and third notches.
At least one element is mounted on the first major surface of the laminated ceramic body.
A cover is arranged such that an opening thereof faces the laminated ceramic body to cover the at least one element described above. The cover includes foot portions disposed in the first and third notches, such that the foot portions are bonded to the respective ground terminal electrodes, thereby fitting the cover to the laminated ceramic body.
In the multilayer ceramic electronic component described above, the cover is preferably made of a metal, and the foot portions and the ground terminal electrodes are preferably bonded to each other via solder or a conductive adhesive.
In addition, the terminal electrodes are preferably defined by dividing terminal via hole conductors.
The first, second, third, and fourth notches are each preferably arranged so as to extend from the first major surface to the second major surface.
Another preferred embodiment of the present invention provides a method for manufacturing the multilayer ceramic electronic component described above, and more particularly, provides a method for manufacturing multilayer ceramic electronic components, each of which includes first, second, third, and fourth notches arranged so as to extend from a first major surface to a second major surface, and terminal electrodes formed by dividing terminal via hole conductors.
The method for manufacturing the multilayer ceramic electronic components according to a preferred embodiment of the present invention includes a step of manufacturing a green mother electronic component is carried out. The green mother electronic component includes a plurality of ceramic green sheets which are laminated to each other and which are provided with the terminal via hole conductors to be formed into the terminal electrodes.
In addition, a second step of forming penetrating holes is performed. The penetrating holes penetrate the green mother electronic component at locations where the terminal via hole conductors are to be divided, thereby exposing the terminal via hole conductors at the internal surfaces of the penetrating holes.
A third step of firing the green mother electronic component is performed.
In addition, a fourth step of dividing the mother electronic component along dividing lines passing through the penetrating holes is performed to obtain a plurality of electronic component bodies. Each of the electronic component bodies is provided with the terminal electrodes formed by the division of the terminal via hole conductors, and the terminal electrodes are provided at main surfaces of notches formed by the division of the penetrating holes.
A fifth step of mounting elements on first major surfaces of the electronic component bodies is performed.
In the first step described above, the terminal via hole conductors are provided for the green mother electronic component such that ground terminal electrodes are formed at main surfaces of the first and third notches provided in a first and third side surface, respectively, of each of the electronic component bodies formed in the fourth step, and a plurality of terminal electrodes arranged in parallel are formed at a main surface of each of the second and fourth notches formed in a second and fourth side surface, respectively.
In addition, in the method for manufacturing the multilayer ceramic electronic components according to a preferred embodiment of the present invention, a sixth step is performed, which includes disposing covers such that openings thereof face the electronic component bodies to cover the respective elements, placing foot portions in the first and second notches, and bonding the foot portions to the ground terminal electrodes such that the covers are fitted to the respective electronic component bodies.
When the first step of manufacturing the green mother electronic component is performed, the first step preferably includes preparing said plurality of ceramic green sheets, providing throughholes in at least one of the plurality of ceramic green sheets for disposing the terminal via hole conductors therein, forming the terminal via hole conductors in the throughholes, forming wiring conductors on at least one of the plurality of ceramic green sheets, and laminating the plurality of ceramic green sheets to each other.
In addition, the fifth step is preferably performed for the electronic component bodies before the fourth step is performed.
Furthermore, the sixth step is preferably performed for the electronic component bodies after the fourth step is performed.
Other features, elements, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the present invention with reference to the attached drawings.